NATE Air Conditioning Certification Full Practice Test 2025

The role of a vapor barrier on insulated supply ducts is to enhance thermal performance. A vapor barrier is designed to restrict the movement of moisture and vapor through the duct material. When properly installed, it prevents condensation from forming on the outside of the ducts, which can occur when warm, moist air comes into contact with cooler surfaces. Preventing this condensation helps maintain the desired temperature of the air moving through the ducts and improves overall energy efficiency.

By containing the thermal energy within the ducts and reducing heat loss or gain, the efficiency of heating and cooling systems is improved, leading to better comfort in conditioned spaces and lower energy costs. Additionally, avoiding moisture accumulation helps mitigate the risk of mold growth and insulation damage, further contributing to the longevity and effectiveness of the HVAC system.